1. Field
Embodiments of the invention generally relate to communications networks and particularly to wireless telecommunications networks, for example, the Universal Mobile Telecommunications System (UMTS), the Global System for Mobile Communications (GSM), the Universal Terrestrial Radio Access Network (UTRAN), the GSM/Edge Radio Access Network (GERAN), Long Term Evolution (LTE), and Evolved UTRAN (E-UTRAN). More particularly, embodiments of the invention relate to methods, apparatuses, computer programs, and a system for timed estimation-based positioning of a user equipment (UE) in LTE systems.
2. Description of the Related Art
Trilateration-based downlink positioning methods, for example, Observed Time Difference of Arrival (OTDOA) in UTRAN, Enhanced Observed Time Difference (E-OTD) in GERAN, and Advanced Forward Link Trilateration (AFLT) in CDMA2000, can be used to determine the position of the UE in relation to a serving cell, for example, an e-UTRAN Node B (eNB) serving the UE.
Neighboring cells, i.e., base stations, mobile stations, etc., can create a significant amount of interference, weakening the signal transmitted between the UE and the eNB and reducing the accuracy of locating the UE in a cellular network. Therefore, trilateration-based downlink positioning methods have been developed and optimized to more accurately determine the position of the UE in relation to the eNB in the cellular network, despite competing interference levels from neighboring cells.
Trilateration-based downlink positioning methods can be used for determining the position of the UE in various applications, for example, in locating an originator of a 9-1-1 emergency call from a mobile station, for example, a wireless telephone. Currently, public safety personnel in the United States estimate that approximately 50% of the 9-1-1 emergency calls that are received daily are placed using wireless telephones. Because of the high volume of 9-1-1 emergency calls placed using wireless telephones, there is a need for increasing the accuracy of determining the position of the UE to timely and accurately locate the individual in need. The Federal Communications Commission (FCC) initiated the “Wireless Enhanced 9-1-1 (E9-1-1) initiative to improve the effectiveness and reliability of wireless 9-1-1 services by providing 9-1-1 dispatchers with additional information on wireless 9-1-1 calls. Under E9-1-1, the FCC requires wireless carriers to provide a local Public Safety Answering Point (PSAP) with the telephone number of the originator of a wireless 9-1-1 call and the location of the cell site or base station transmitting the call. The FCC, under E9-1-1, also requires wireless carriers to provide the position of the wireless telephone originating the 9-1-1 emergency call within 50 meters for 67% of the calls and within 150 meters for 95% of the calls.